Process for preparing benzalaniline-3-sulfonic acid compounds



United States Patent-Oil 2,798,090 Patented July 2, 1957 FOR PREPARING BENZALANILINE-S- ULFONIC ACID COMPOUNDS Max W. Krell and Flaven E. Johnson, Kingsport, Tenm, assignors to Eastman Kodak Company, Rochester, N. Y., a corporation of New Jersey No Drawing. Application March 2, 1953, Serial No. 339,923

12 Claims. '(Cl. 260-509) PROCESSS This invention relates toan. improved process for preparing benzalaniline-3-sulfonic' acid compounds which in their free acid form have the formula:

stands in paraposition to the H C==N grouping grouping.

It is an object of this invention to provide an improved process for preparing benZalaniline-3-sulfonic acidcompounds having the formula above given, whereby these compounds are efiiciently and. economically prepared in good yield. A particular object is to provide a new and improved process for preparing said benzalaniline-3- sulfonic acid compounds using nitrobenzene -as a starting compound.

4- (ethyl, ,B hydroxyethyl) aminob enzalan'iline-3 -sulfonic acid, 4-(butyl, p-hydroxyethyl)aminobenzaianiline iisulfonic acid and 4-(butyl, B-hydroxyethyl) amino-2'- methylbenzalaniline-3-sulfonic1acid have been prepared by reacting N-ethyl-N-B-hydroxyethylaniline,'N-butyl-N- fl-hydroxyethylaniline and N-butyl-N-B hydroxyethyl mtoluidine, respectively, with formaldehyde and sodium meta-nitrobenzene sulfonatein the presence 'of:hydrochloric acid and iron. Dippy, Hogarth, Watson and Williams, J. Soc..Chem. Ind., vol. 56, pages 346T.348T (1937).

Wehave discovered that the benzalaniline-3-sulfonic acid compounds having the formula numbered I: canJbe prepared by reacting aniline compounds 'having 'the formula:

wherein X, R and R1 have the meaning previously assigned to them'with formaldehyde and meta-nitrobenzene sulfonic acid in the presence of sulfuric acid. and iron. The aniline compound is not substituted in the para position to the amino group. The use of sulfuricacid in place of hydrochloric acid gives. much better yields and results in much lower costs for producing these products. Additionally, the use of sulfuric acid rather than hydrochloric acid considerably reduces the problem of corrosion.

A particular feature of our invention is that nitrobenzene can be sulfonated to meta-nitrobenzene sulfonic acid and the meta-nitrobenzene sulfonic acid thus formed is used :without isolation from its reaction mixture in the preparation of the benzalaniline-3-sulfonic acid compounds. This is a big improvement over the hydrochloric acid process wherein meta-nitrobenzene sulfonic acid is formed by sulfonating nitrobenzene with sulfuric acid,

isolated from its reaction mixture, and then reacted with formaldehyde and an aniline compound in the presence of hydrochloric acid in that the meta-nitrobenzene sulfonic acid does not have to be separately recovered and the sulfuric acid present in the sulfonation operation supplies the sulfuric acid used in thereaction between the aniline compound, formaldehyde and meta-nitro benzene sulfonic acid. Additionally, the advantages above enumerated withrespect to better yields, lower costs and reduced corrosion are alsoobtained.

The reaction between the aniline compound, formaldehyde and meta-nitrobenzene sulfonic acid in the presence of sulfuric acid and iron is'preferably carried: out at a temperature offrom 5 C. to C. A temperature of from about 16 C. to about 20 C. appears to be especially advantageous. Similarly, the iron is preferably .added.-.as fast as foaming and temperature control will permit and preferably should not take over 3 hours. Followingthe conditions just set forth, product yields of 80% or more are normally obtained. The reactionrhas been carried out at temperatures as low as 0 C. and as high as C. with the addition of iron taking up to 8 hours Jbut conditions falling outside the preferred range ordinarily give much inferior results to those obtained -when the prefered conditions are employed.

The aryl nucleus X may be substituted by substituents such as, for example, the methyl group, the ethyl group, a methoxy group, an-ethoxy group, a chlorine atom or a bromine atom. Illustrative of the alkyl groupsrepresented by R and R1 are the methyl, the ethyl, the n-propyl,

.the isopropyl and the n-butyl groups. Illustrative of the hydroxyalkyl groups represented by R and.R are the ii-hydroxyethyl group, the p-hydroxypropyl gro p. the

. -hydroxypropyl group, the ,8,-, -dihydroxypropyl group and the 6-hydroxybutyl group. Similarly, the ,B-methoxyethyl and the fi-ethoxyethyl groups are illustrative of the alkoxyalkyl groups R and R1 represent.

. Illustrative of the aniline compounds having the formula numbered II are N,N-di-[i-hydroxyethylaniline,

N ,N-di-fl-hydroxyethyl-rn-toluidine, N,N di fl-hydroxyethyl m ethylaniline, N-ethyl-N-B-hydroxyethylaniline, N,N -'dimethylaniline, N,N diethylaniline, N,N di n- -propylaniline, N,N-di-n-butylaniline, N,N-di-B-methoxyethylaniline, N,N-di-B-ethoxyethylaniline, N,N-di-fl-hydroxyethyl-m-chloroaniline, N,N di ,B-hydroxyethyl-mmethoxyaniline, N-ethyl-N-B-hydroXyethyl-m-toluidine,

m-toluidine, N,N-di-;8, -dihydroxypropyl-m-toluidine, N- rnethyl-N- -hydroxyethyl-m-toluidine, N,N-di-p-hydroxyethyl-m-bromoaniline, N,N-di-y-hydroxypropyl-m-bromoaniline, and N,N-di-B-hydroxybutyl-m-chloroaniline.

The following examples, in which parts are expressed 'as parts by weight, illustrate the process of our invention.

Example 1 l23tparts of nitrobenzene were slowly added with good agitation to 460 parts of 20% oleum at 50 C. .By .the ftime'addition of the nitrobenzene was complete the .temperature of the reaction mixture had risen to .C.- C. Following the addition of ,the .nitrobenzenethe obtained.

3 reaction mixture was heated very slowly to 95 C. and maintained at 95 C. for two hours after which it Was allowed to cool to room temperature.

214 parts of the meta-nitrobenzene sulfonic acid reaction mixture prepared as described above were added to 545 parts of water and then 49 parts of N,N-di-fihydroxyethyl-m-toluidine were dissolved in the resulting mixture. The reaction mixture thus obtained was cooled to 20 C. and 27 parts of 36% aqueous formaldehyde were added thereto. 56 parts of iron filings were then added to the reaction mixture during approximately two hours while maintaining the temperature between 16 C. and 20 C. After the iron addition was complete, the reaction mixture was stirred for four hours at 16 C.- 20" C. and then filtered after decanting the reaction mixture from any unreacted iron. 4-(di-,8-hydroxyethylamino)-2'-methylbenzalaniline-3-su1fonic acid having the formula:

-- HOOHzCHz l e v I CH3 SOaH was recovered as an orange solid, washed well with water and dried. 85.5 parts (90% yield) of dried product were Example 2 By use of 45 parts of N,N-di-fi-hydroxyethylaniline in placeof N,N-di-fkhydroxyethyl-m-toluidine in Example 1, 81 parts (89% yield) of 4'-(di-fi-hydroxyethylarnino)- henzalaniline-3-sulfonic acid were obtained.

Example 3 Example 1 was repeated using 41 parts of N-ethyl-N- fi-hydroxyethylaniline in place of N,N-di-fi-hydroxyethylm-toluidine. About 70 parts (80% yield) of 4'-(ethyl, fl-hydroxyethyl)aminobenzalaniline-3-sulfonic acid were obtained.

Example 4 31 parts of concentrated sulfuric acid were added to 374 parts of water and 49 parts of N,N-di-B-hydroxyethylm-toluidine were dissolved in the resulting mixture. The solution thus obtained was cooled to 15 C. and 27 parts of 36% aqueous formaldehyde were added. 247 parts of dilute sulfuric acid were then added, the dilute acid consisting of 169 parts of water and 78 parts of concentrated sulfuric acid. Next, 87.5 parts of sodium m-nitrobenzenesulfonate trihydrate were added and then 56 parts of iron filings were added over a period of approximately 2% hours while maintaining the temperature of the reaction mixture at 16 C.20 C. After completion of the iron addition, 75 parts of concentrated sulfuric acid were added over a period of 2% hours while still maintaining the temperature of the reaction mixture at 16 C.20 C. After completion of the acid addition, the reaction mixture was stirred for two hours at a temperature of 16 C.20 C., following which it was decanted to separate it from unreacted iron and filtered. The product, 4'-(di B hydroxyethylamino)-2-methylbenzalaniline-3-sulfonic acid, was recovered on the filter as an orange solid. It

was washed several times with cold water and dried. 76

parts 80% yield) of dried product were obtained.

I Example 5 214 parts of m-nitrobenzene sulfonic acid-sulfuric acid prepared as described in Example 1 were added to 545 parts of water and then 54 parts of N,N-di-[i-hydroxyethyl-m-chloroaniline were dissolved in the resulting mixture. The reaction mixture thus obtained was cooled to 20 C. and 27 parts of 36% aqueous formaldehyde were added thereto. 56 parts of iron filings were added to H the reaction mixture over a period of approximately two hours while maintaining the temperature between 16 C. and 20 C. After the iron addition was complete, the

line compound from which it is prepared is given.

Benza1aniline-3-Snlfonic Acid Compound Aniline Compound 6. 4' (d1 B hydroxyethylamino) 2 methoxybeuzalaniliue-3Fsu1fonic acid. 7. 4 (di B hydroxyethylamino) 2' eth0xybenzaJaniline-3-sulfonic acid.

8. 4 (di B hydroxyethylamino) 2' ethylbenzalanilinerii sulfonic acid.

9. 4 (dimethylamino) benzalanihue-iisulfonic acid.

10. 4 (dimethylamino) 2 methylbenzal-aniline-3sulfonic acid.

11. 4 (diethylamino) 2 methylben zal-anilineB-sulfonic acid.

12. 4 (d1 n propylamiuo) benzalaniline-3-sulionic acid.

13. 4 (di n butylamino) benzalaniline-3-sulfonic acid.

14. 4 (di 6 methoxyethylamino) 2'- methylbeuzalaniliue-3-sulfonic acid.

15. 4 (di- 13- ethoxyethylamino) benzalaniline-3-sulfonic acid.

16. 4 (ethyl, ,8 hydroxyethyl) ammobenzalaniline-B-sulfonic acid.

17. 4 (n propyl, B hydroxyethyl) aminobenzalaniline-lisulfonic acid.

18. 4 (n butyl, p8 hydroxyethyl) amino-benzalanilinefi-sulionic acid.

19. 4 (ethyl, 'yhydroxypropyl) ammobenzalaniline-3-sulfonic acid.

20. 4 (ethyl, 5 hydrcxybutyl) ammobenzalaniline-3-sulionic acid.

21. 4 (methyl, fl-hydroxyethyl) amino- 2-methylbenzalaniline-3-sulfonic acid.

22. 4 (di B hydroxyethylamino) 2- brom0benzalaniliue-3-sulfonic acid.

23. 4' (di- 'yhydroxypropylamino) 2'- bromobenzalaniline-B-sulionic acid.

24. 4 (di 5 hydroxybutylamino) 2- chlorobenzalaniline-S-sulfouic acid.

25. 4- (ethyl, 3, dihydroxypropyl) aminod- 2 methylbenzalaniline-3-sulfou1c aci 26. 4 (ethyl, 5,7- dihydroxypropyl) amino-benzalaniline-3-sulionic acid.

27. 4 (di 5, dihydroxypropylamino)- 2'-methylbenzalaniline-B-sulfonic acid.

28. 4 (nbutyl, 6, dihydroxypropyhamino 2 methylbenzalanilme 3 sul- N,N di B hydroxyethylm-methoxyaniline.

N,N di B hydroxyethylrn-ethoxyaniline.

N ,N di B hydroxyethylm-ethylaniline.

N,N-dimethylaniline.

N,N dimethylamino m toluidine.

N,N diethylaim'no mtoluidine.

N,N-di-n-propylaniline.

N,N-di-n-butylaniline.

N,N di B methoxycthylm-toluidine.

N,N d1 B ethoxyethylaniline.

N ethyl N B hydroxyethylaniline.

N-n-propyl-N-fl-hyoroxyethylaniline.

N- nbutyl- N ,8- hydroxyethylaniline.

N ethyl N -y hydroxyprcpylaniline.

N ethyl N 6 hydroxybutylaniline.

N methyl N B hydroxyethyl-m-toluidine.

N,N di B hydroxyethylm-bromoanjline.

N,N di 'yhydroxypropylmbromoaniline.

N ,N (1i 6 hydroxybutylm-chloroaniline.

N ethyl N BH- dillydroxypropyl-m-toluidine.

N-ethyl-N-fl dihydroxypropylaniline.

N,N di 8, dihydroxyprcpyl-m-toluidine. e

N -n-but;yl-N-B,7- dihydroxypropyl-m-toluidine.

ionic acid.

29. 4 (n butyl, B hydroxyethyl) amiuo 2 methylbenzalaniline 3 sultonic acid.

N-nbutyl- N-B-hydroxyethyl-m-toluidine.

The benzalaniline-3-sulfonic acid compounds prepared in accordance with the process of .our invention are not broadly new. They are useful, for example, in the preparation of methine compounds, such as those described in U. S. Patents 2,583,551 and 2,583,614, issued January 29, 1952, which are valuable dyes for cellulose acetate textile materials. Thus, following the procedure described in U. S. Patents 2,583,551 and 2,583,614 the benzalaniline-3-sulfonic acid compounds are useful, for example, in the preparation of methine compounds having the formula:

(III) R\ ON or the formula:

(IV) R ON N O=C R1 000R:

R and R1 have the meaning previously assigned to them, R2 represents an alkyl group having one to four, inclusive,

carbon atoms, a fi-methoxyethyl group or a p-ethoxyethyl group and Y represents a methyl group, an ethyl group, a methoxy group, an ethoxy group, a chlorine atom or a bromine atom. These compounds are dyes for cellulose acetate textile materials.

While the prior art teaches that when 4'-substituted aminobenzalaniline-3-sulfonic acid compounds are used to prepare methine dyes the reaction should be carried out in an organic solvent such as 50% aqueous methyl alcohol, we have discovered that the reaction can be carried out using water as thereaction medium. The use of water is advantageous in that it eliminates a solvent recovery operation and involvesthe use of-a non flammable inert diluent rather than a flammable inert diluent.

In accordance with our discovery methine compounds having the formula:

Q1 z wherein Q represents a hydrogenatom, an alkyl group, a hydroxyalkyl group or an alkoxyalkyl group, Q1 represents an alkyl group, a hydroxyalkyl group or an alkoxyalkyl group, X represents a monocyclicar yl nucleus of the benzene series and Z represents acyano group or a stands in para position to the are prepared by reacting a benzalaniline-3-sulfonic acid having the formula:

(V Q t sour wherein Q, Q1 and X have the meaning previously assigned to them and the \N group stands in para position to the H -C=N group with malononitrile, an alkyl cyanoacetate or an alkoxyalkyl cyanoacetate in water in the presence of an acid binding agent. The reaction can be carried out at a temperature of from about 0 C. to about 100 C. However, a temperature of from about 20 C. to about 50 C. appears to give the best results and is preferred.

Acid binding agents that can be used include, for example, sodium bicarbonate, sodium carbonate, potassium bicarbonate and potassium carbonate. Slightly improved yields and a smoother reaction mixture result when a wetting agent is employed in the reaction although good yields have been obtained when none was used. Only a small amount of wetting agent need be used to obtain the benefits just mentioned. While all wetting agents have not been tried, it appears that any wetting agent whether anionic, nonionic or cationic can be used. Duponal, a long chain aliphatic alcohol sulfate, is representative of the anionic wetting agents that can be used while Triton X-l00 which is made by condensing an alkyl phenol with ethylene oxide is representative of the nonionic wetting agents.

The following examples in which parts are expressed as parts by weight illustrate the manner in which the prepare methine compounds.

Example 30 V 378 parts of 4-(di-fl-hydroxyethylamino)-2-methylbenzalaniline-3-sulfonic acid were placed in 3200 parts of water and 92 parts iof-sodium bicarbonate were added thereto. The reaction mixture resulting was heated slowly to 60 C. and stirred until solution was complete. parts of methylcyanoacetate were then added after adding two parts of a wetting agent. The reaction mixture thus obtained was stirred for 1.6 hours without heating and the product which forms was recovered on the filter by filtration. The yellow crystalline product collected on the filter was washed well with cold water and then dried. 252 parts (82.9% of theory) of 4-(di -p-hydroxyethylamino) 2 methylbenzylidenemethylcyanoacetate having the formula:

HOGHIOHI 0N were thus obtained. It melts at 143 C.150 C.

- Example 31 Bythe use of 364 parts of 4'-(di-p-hydroxyethylaminoy beuzalaniline-3-sulfonic acid in place of 4'-(di-[3-hydroxyethylamino) -2-methylbenzalaniline-3-sulfonic acid in Example 30, 225 parts (77.6% of theory) of 4- (di-,B-h droxyethylamino -benzylidenemethylcyanoacetate melting Example 32 This reaction was carried .out in the same manner as that described in Example 30 except that 348 parts of 4-(ethyl, B hydroxyethyl)aminobenzalaniline-3-su1fonic acid were used inplace of 4'-(di-fi-hydroxyethylamino)- 2-methylbenZalaniline-3-sulfonic acid. The dye com pound obtained separates as an oil which solidifies upon standing.

164 parts (60% of theory) of 4-(ethyl, 13 hydroxyethyl) aminobenzylidenemethylcyanoacetate melting at 76". C.-78 C. were obtained.

Example 33 378 parts of 4'-(di-B-hydroxyethylamino)-2-methyl- .benzalaniline-sulfonic acid were placed in 3200 parts of water and 92 parts of sodium bicarbonate were added.

The reaction mixture thus obtained was heated slowly to :iEI OC HaCfig CHa were obtained. It melts at 138 C.-140 C.

Example 34 By the use of 140 parts of ethylcyanoacetate in place of methylcyanoa-cetate in Example 30, a good yield of 4- (di B hydroxyethylamino) 2 methylbenzylideneethylcyanoacetate having the formula:

110 among H /ON N o=o\ HO CHzC: 0-0 CZHE H: ll I I o is obtained.

p Example 36 By the use of 185 parts of )S-methoxyethylcyanoacetate in place of methylcyanoacetate in Example 31, a good yield of 4-(di-fi-hydroxyethylamino)benzylidene-fi-methoxyethylcyanoacetate having the formula; 7

HO CH CHz N N 0:0 4' Hoomo 1 ([If-OOHgOHgOCHa 1s obtamed.

The methine compounds set forth in the tabulation given hereinafter are likewise readily prepared in accordance with the improved procedure described hereinbefore.' e

37. 4 dimethylamino 2 methylbenzylidenemethylcyanoacetate 38. .4 diethylaminobenzylidenemethylcyanoacetate 39. 4 (di methoxyethylamino) 2 methylbenzylidenemethylcyanoacetate 40. 4 (di B ethoxyethylamino)benzylidenemethylcyanoacetate 41. 4 (di ,B hydroxyethylamino') 2 chlorobenzylidenemethylcyanoactate 42. 4 r (n butyl, ,8 hydroxyethyl)aminobenzylidene methylcyanoacetate 43. 4 methylaminobenzylidenemethylcyanoacetate 44.4 ethylamino 2 methylbenzylidenemethylcyanoacetate 45. 4 n butylaminobenzylidenemethylcyanoacetate 46. 4 (di ,8 hydroxyethylamino) 2. chlorobenzylideneethylcyanoacetate 47. 4 (ethyl, B hydroxyethyl):aminobenzylidene npropylcyanoacetate 48. 4 (ethyl, [3 hydroxyethyl)aminobenzylidene nbutylcyanoacetate 49. 4 (di p hydroxyethylamino) 2 methylbenzylidene B ethoxyethylcyanoacetate 50. 4 (di ,6 4 hydroxyethylamino) 2 chlorobenzylidenemalononitrile 51. 4 (ethyl, .B-hydroxyethyl)aminobenzylidenemalononitrile 52. 4 (n butyl, malononitrile 5 3. 4 dimethylaminobenzylidenemalononitrile 54. 4 (di p hydroxyethylam-ino) 2 methoxybenzylidenemalononitrile 55. 4 (di 13 hydroxyethylamino) 2 ethoxybenzyl idenemalononitrile 56. 4 (di B hydroxyethylamino) 2 ethylbenzylidenemalononitrile 57. 4 (di p hydroxyethylamino) 2 bromobenzylidenemalononitrile 58. 4 (di 13 methoxyethylamino)benzylidenemalononitrile B hydroxyethyl)aminobenzylidene- Any of the unacylated 'methine dye compounds disclosed in U. S. Patents 2,583,551 and 2,583,614 can be "prepared using the improved procedure described herein.

The methine compounds containing a hydroxyalkyl group can be acylated in accordance with the procedure described in U. S. Patents 2,583,551 and 2,583,614 to obtain acylated methine dye compounds.

So far as we are aware, the new and improved processes described herein for the preparation of the benzalaniline- 3-sulfonic acid compounds and the methinecompounds l are operable regardless of the size of the alkyl, hydroxyalkyl or alkoxyalkyl group involved. However, those compounds wherein the alkyl group contains one to four, inclusive, carbon atoms, the hydroxyalkyl group contains twotofour, inclusive, carbon atoms and the alkoxyalkyl group contains three ,to four, inclusive, carbon atoms appear to be the most practical and useful and, accordingly, our invention is especially directed to such benzalaniline-S-sulfonic acid and methine compounds. Illustrative alkyl, hydroxyalkyl and alkoxyalkyl groups have been specificallydisclosed in connection with the members R and R1.

The methine compounds described herein are valuable dyes for cellulose acetate textile materials. They may be advantageously directly applied to the cellulose acetate textile material undergoing coloration in the form of an aqueous suspension which. can be prepared by grinding the dye to a paste in the presence of a sulfonated oil, soap, sodium lignin sulfonate or other suitable dispersing agent and dispersing the resulting paste in water.

Direct dyeing operations can with advantage be conducted at temperatures of about 70 C.- C. but any suitable temperature can be used. Thus, the cellulose acetate textile material to be dyed or colored is ordinarily added to the dye bath at a temperature lower than that at which the main portion of the dyeing is to be effected, a temperature approximating 45 C.-55 C., for example, following which the temperature is raised to that selected for carrying out the dyeing operation. The temperature at which the dyeing is conducted may, of course, be varied somewhat depending upon the particular cellulose acetate textile material undergoing coloration and the particular amount of coloration desired. As understood by those skilled in the dyeing art, the intensity of dyeing can be varied by varying the proportion of dye to material undergoing coloration. The amount of dye used can be, for example, /3% to 3% (by weight) of that of the cellulose acetate textile material although lesser or greater amounts of dye can be used.

We claim:

1. The process for preparing benzalaniline-3-sulfonic acid compounds which in their free acid form have the formula:

8 OaH stands in para position to the H -C=N grouping which comprises reacting an aniline compound having the para position to the amino group free and having the formula wherein R, R1 and X have the meaning previously assigned to them, with formaldehyde and meta-nitrobenzene sulfonic acid in the presence of sulfuric acid and iron at a temperature of from 5 C. to 35 C.

2. The process'for preparing benzalanilineQ-sulfonic acid compounds which in their free acid form have the formula wherein X stands for a monocyclic aryl nucleus of the benzene series and R and R1 each represents :a member selected from the group consisting of an alkyl group, a hydroxyalkyl group and an alkoxyalkyl group and wherein the group stands in para position to the H C=N grouping which comprises reacting an aniline compound having the para position to the amino group free and having the formula N-X R1 wherein R, R1 and X have the meaning previously assigned to them, with formaldehyde and meta-nitrobenzene sulfonic acid in the presence of sulfuric acid and iron at a temperature of from about 16 C. to about 20 C. 3. The process for preparing benzalaniline-S-sulfonic acid compounds which in their free acid form have the formula:

wherein X stands for a monocyclic aryl nucleus of the benzene series and R and R1 each represents a member selected from the group consisting of an alkyl group, a hydroxyalkyl group and Ian alkoxyalkyl group and wherein the group stands in para position to the H C=N grouping which comprises forming metanitrobenzene sulfonic acid by reacting nitrobenzene with an excess of sulfuric acid over that theoretically required to form meta-nitrobenzene sulfonic acid and reacting the meta-nitrobenzene sulfonic acid thus formed without isolation from its reaction mixture with formaldehyde and an aniline compound having the para position to the amino group free and having SOaH 10 wherein X stands for a monocyclic aryl nucleus of the benzene series and R and R1 each represents a member eelected-from the group consisting of an alkyl group, a .hydroxyalkyl group and an alkoxyalkyl group and wherethe group stands in para position to the H -O=N grouping which comprises forming metanitrobenzene sulfonic acid by reacting nitrobenzene with an excess of sulfuric acid over that theoretically required to form meta-nitrobenzene sulfonic acid and reacting the meta-nitrobenzene sulfonic acid thus formed without isolation from its reaction mixture with formaldehyde and an aniline compound having the para position to the amino group free and having the formula wherein R, R1 and X have the meaning previously as signed to them, in the presence of iron at a temperature of from about 16 C. to about 20 C.

5. The process for preparing 4' (di-[i-hydroxyethylamino) 2 methylbenzalaniline 3 sulfonic acid which comprises reacting N,N-di-B-hydroxyethyl-rn-toluidine with formlaldehyde and meta-nitrobenzene sulfonic acid in the presence of sulfuric acid and iron at a temperature of from 5 C. to 35 C.

6. The process for preparing 4'(di-;8-hydroxyethylamino)-2-methylbenzalaniline-3-sulfonic acid which comprises reacting N,N-di-B-hydroxyethyl-m-toluidine with formaldehyde and meta-nitrobenzene sulfonic acid in the presence of sulfuric acid and iron at a temperature of from about 16 C. to about 20 C.

7. The process for preparing 4-(di-B-hydroxyethylamino)-2'-Inethylbenzalaniline-3-sulfonic acid which comprises forming meta-nitrobenzene sulfonic acid by reacting nit-robenzene with an excess of sulfuric acid over that theoretically required to form meta-nitrobenzene sulfonic acid and reacting the meta-nitrobenzene sulfonic acid thus formed without isolation from its reaction mixture with formaldehyde and N,N-di- 3'hydroxyethyl-mtoluidine in the presence of iron at a temperature of from 5 C. to 35 C.

8. The process for preparing 4-(di-p-hydroxyethylamino)-2-methylbenzalaniline-3-sulfonic acid which comprises forming meta-nitrobenzene sulfonic acid by reacting nitirobenzene with an excess of sulfuric acid over that theoretidally required to form meta-nitrobenzene sulfonic acid and reacting the meta-nitrobenzene sulfonic acid thus formed without isolation from its reaction mixture with formaldehyde and N,N-'di-B-hydroxyethyl-mtoluidine in the presence of iron at a temperature of from about 16 C. to about 20 C.

9. The process for preparing 4'-(di-Bhydroxyethylamino)benzalaniline-3-sulfonic acid which comprises reacting N,N-di-B-hydroxyethylaniline with formaldehyde and metanitrobenzene sulfonic acid in the presence of sulfuric acid and iron at a temperature of from 5 C. to 35 C.

10. The process for preparing 4-(ethyl, fi-hydroxyethyl)-a rninobenzalaniline-3-sulfonic acid which comprises reacting N-ethyl-N-fl-hydroxyethylaniline with formaldehyde and meta-nitrobenzene sulfonic acid in the presence of sulfuric acid and iron at a temperature of from 5 C. to 35 C.

11. The process for preparing 4-(di- 3-hydroxyethylamino)-2-chlorobenzalaniline-3-sulfonic acid which comprises reacting N,N-di-B-hydroxyethyl-m-chloroaniline with formaldehyde and meta-nitrobeuzene sulfonic acid 11 t p I p N p 12 in the presence of sulfuric acid and iron at a temperature References Cited in the file of this patent of from to 0 r UNITED STATES PATENTS 12. The process for preparing 4'-(n-buty1, fi-hydroxy- 'ethyl)amino-2-methylbenzalaniline-3- u1fonic acid which 2,048,006 m y 21, 1 comprises reacting N-n-butyl-N-fl-hydroxyethyl-m-to1ui- 5 2,583,551 Dlckey et 29, 1952 dine with formaldehyde and meta-*nitrobenzene sulfo ic 2,583,614 q f 31 1952 acid in the presence of sulfuric acid "and iron at a tem- FOREIGN PATENTS Pemture fmm 586,127 Great Britain Mar. 7, 1947 

1. THE PROCESS FOR PREPARING BENZALANILINE-3-SULFONIC ACID COMPOUND WHICH IS THEIR FREE ACID FORM HAVE THE FORMULA: 